This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-049667, filed Feb. 25, 2000, the entire contents of which are incorporated herein by reference.
The present invention relates to a method for manufacturing a semiconductor silicon (Si) single crystal for use in manufacturing process of a large-scale integrated circuit (LSI).
At present, the Si single crystal for use in the LSI manufacturing process is usually formed with a Czochralski (CZ) process or Floating Zone (FZ) process. To be more specific, most of the Si single crystals are formed with the CZ process. The CZ process is a method of growing the Si single crystal by bringing a seed crystal into contact with a Si melt (this step is called a xe2x80x9cdipping processxe2x80x9d) and pulling the seed crystal. The FZ process is a method of growing the Si single crystal by heating an end of a raw-material rod formed of polycrystalline Si to melt it, bringing a Si seed crystal into contact with the melted portion, and moving the molten zone along the length of the rod.
In the CZ method, a necking process proposed by W. C. Dash in 1959 is employed to grow a dislocation-free single crystal. The necking process is performed after the dipping process to form a long, thin neck portion of 3-5 mm in diameter. The necking portion prevents the dislocations, which are generated in the seed crystal due to thermal shock during the dipping process, from propagating into the grown crystal. Thus, the necking process is an effective process for growing the dislocation-free single crystal. However, the probability of growing the dislocation-free single crystal with the necking process is not always 100%. In addition, the long, thin neck portion cannot support a large single crystal of not less than 100 kg weight which has been recently required in the LSI manufacturing process. The FZ process also uses the necking process so that it has the same problems described above.
An object of the present invention is to provide a method for manufacturing a dislocation-free silicon single crystal without employing a necking process.
According to the present invention, there is provided a method for manufacturing a dislocation-free silicon single crystal, comprising the steps of:
preparing a silicon seed crystal formed of a dislocation-free single crystal having a boron concentration of 1xc3x971018 atoms/cm3 or more;
preparing a silicon melt having a boron concentration which differs from that of the seed crystal by 7xc3x971018 atoms/cm3 or less; and
bringing the seed crystal into contact with the silicon melt to grow the silicon single crystal.
In the present invention, the silicon single crystal is preferably grown in accordance with a Czochralski process or a Floating Zone process.
In the present invention, the boron concentration of the seed crystal preferably ranges from 1xc3x971018 atoms/cm3 to 7xc3x971018 atoms/cm3, and more preferably 3xc3x971018 atoms/cm3 to 5xc3x971018 atoms/cm3.
Furthermore, in the present invention, the silicon melt is preferably boron undoped.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.